This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
3GPP third generation partnership project
AP access point
AFH adaptive frequency hopping
BLER block error rate
BS base station
CA carrier aggregation
CC component carriers
CCA clear channel assessment
CM coexistence manager
COT channel occupancy time
CQI channel quality indicator
CSMA carrier sense multiple access
DAA detect and avoid
eNodeB base station of a LTE/LTE-A system
ETSI European Telecommunications Standards Institute
FCC federal communications commission
FHSS frequency hopping spread spectrum
ID identifier
IEEE Institute for Electrical and Electronics Engineers
IP Internet protocol
ISM industrial, scientific and medical
LBT listen-before-talk
LBTx listen-before-transmit
LTE long term evolution (of the evolved UTRAN system)
LTE-A long term evolution-advanced
MAC medium access control
Non-LBT non-listen-before-talk
Non-LBTx non-listen-before-transmit
PCell primary serving cell
RAT radio access technology
RRC radio resource control
SCells secondary serving cells
SIB system information block
TV WS television white spaces
UE user equipment
UTRAN universal terrestrial radio access network
WLAN wireless local area network
The capacity of wireless networks has consistently increased over the last decade due an increase in numbers of wireless users utilizing those networks. In addition, network capacity is on the rise due to the ever-increasing volume of content rich data (i.e. streaming HD video) transmitted and received on wireless networks. To accommodate this increase in capacity, network operators as well as manufacturers of user handsets and network equipment will in the near future seek to deploy 4th Generation (4G) wireless networks according to the Long Term Evolution-Advanced (LTE-A) standard. LTE-A cellular networks will require minimum support of 1 Gbps and 100 Mbps peak rates for low-mobility and high-mobility users, respectively. Hence, network operators, as well as manufacturers of user handsets and network equipment, seek methods, devices and computer programs to handle increase capacity on wireless networks to avoid congestion.
Radio access technology (RAT) deployed in legacy 3rd Generation (3G) wireless networks as well as LTE/LTE-A networks conventionally transmit and receive wireless communications on licensed frequency spectrum in limited spectral bands designated according to the country in which they operate. Obtaining the licensed frequency spectrum involves significant costs. Accordingly, wireless network operators compete to purchase licensed frequency spectrum to accommodate users and their data based upon the network capacity to avoid congestion.
To control costs and to avoid congestion, network operators, as well as manufacturers of user handsets and network equipment, have sought to off-load some wireless traffic to non-cellular networks. For example Internet traffic can be offloaded to available WLAN whose access points provide access to the Internet. This source alone is not expected to fully offset predicted increases in wireless data traffic as well as meet the above stated minimum peak data rates under LTE-A.
Another approach to address congestion in 4G wireless networks, such as cellular core networks in LTE-A, is to off-load traffic on available unlicensed frequency spectrum. This approach takes advantage of so-called Carrier aggregation (CA) undergoing development for the LTE/LTE-A systems. In CA, the whole system bandwidth is carved into multiple groupings of “component carriers” (CCs), each up to 20 MHz, so that LTE-A devices are able to use wider bandwidth of up to 100 MHz, while at the same time allowing LTE devices to continue viewing the spectrum as separate component carriers. Specific for LTE/LTE-A, each user equipment (UE) is to be assigned one primary serving cell (PCell) which remains active and one or more secondary serving cells (SCells) which may or may not be active at any given time, depending on data volume for the UE and traffic conditions in the serving cell. At least one CC in the system is to be backward compatible with UE's which are not capable of CA operation.
These non-licensed frequency spectrum or licensed-exempt bands vary by region and typically are allocated to frequency bands such as 315-470 MHz, 868-870 MHz, 902-928 MHz and referred to as the Industrial, Scientific and Medical bands (ISM). Additional unlicensed frequencies were opened in 2008 in the United States by the Federal Communication Commission. Those newly opened unlicensed frequencies where unused broadcast TV spectrum allocated at 300 MHz to 400 MHz (so-called “TV white space”). Another popular and internationally designated licensed-exempt band is the 2.4 GHz frequency band which actual covers wireless operations in the 2400-2483.5 MHz frequency range. The 2.4 GHz frequency band often hosts for standardized and proprietary protocols such as IEEE 802.11b/a/g/n/ac, WiFi, Bluetooth®, or ZigBee™.
Operation on the unlicensed 902-928 MHz and 2.4 GHz frequency bands are subject to regulation or possible future adherence to standardization depending upon the region of operation. These regulation or standardization seeks to manage co-existence in the unlicensed bands to provide spectrum access to facilitate spectrum sharing among varying equipment. For example, in the United States operations in the 2400-2483.5 MHz frequency range must adhere to Title 47, Telecommunication, Chapter 1, Part 15, radio devices as introduced by the Federal Communications Commission in 2001. According to that regulation, operations in the 2400-2483.5 MHz frequency range must employ frequency hopping spread spectrum (FHSS) with at least 75 hopping frequencies and at different transmission power levels. According to FCC part 15.247, channel carrier frequencies are separated by a minimum of 25 kHz or a 20 dB bandwidth of a hopping channel, whichever is greater. Also required is a maximum 20 dB bandwidth of the hopping channel which is 1 MHz. The average time of occupancy cannot be greater than 0/0.4 seconds within a 30 second period. Moreover, hopping tables are required to have a pseudo-randomly ordered list of hopping frequencies and each frequency must be used equally on the average by each transmitter.
In Europe, currently under consideration before the European Telecommunications Standards Institute (ETSI), is a more stringent requirement for radio systems co-existent in the 2.4 GHz frequency band. Under this proposed standard opportunistic spectrum sharing would be required to employ adaptive frequency hopping (AFH) (or wide band modulation other than FHSS) equipment employ a detect and avoid (DAA) mechanism which would allow user equipment to adapt to its environment by identifying frequencies that are being used by other equipment.
One DAA mechanism using LBT operates by designating a hopping frequency ‘unavailable’ when a signal is detected prior any transmission on that frequency. In particular, at the start of every dwell time, before transmission on one of fifteen (15) hopping frequencies, the equipment performs a clear channel assessment (CCA) to detect for energy. The observation time is less than 0.2% of a channel occupancy time (COT) with a minimum of 20 μs. Accordingly, if the user equipment finds the hopping frequency clear transmissions can commence. On the other hand, if a signal is present with a level above a detection threshold the hopping frequency is designated unavailable. The detection threshold is required to be proportional to the transmit power of the transmitter. For example, given a 20 dB transmitter, the detection threshold level is equal or lower that 70-dB/MHzat the input to the receiver (assuming 0 dB receiving antenna). The removal of a hopping frequency by designating it unavailable requires adding a hopping frequency to maintain the fifteen (15) hopping frequencies.
Such, a DAA mechanism provides that control over access to radio resources is distributed among the radio systems, so that those radio systems can achieve a fair sharing of radio resources to some extent.
Alternatively, adaptive frequency hopping equipment can employ a different DAA mechanism. These mechanisms operate by designating a hopping frequency ‘unavailable’ when interference is detected during transmissions on that frequency. In particular, during normal operation, the equipment evaluates the presence of a signal on each of available fifteen (15) hopping frequencies. If a signal is present with a level above the detection threshold the hopping frequency is designated “unavailable.” The detection threshold is required to be proportional to the transmit power of the transmitter. For example, given a 20 dB transmitter, the detection threshold level is equal or lower that 70-dB/MHz at the input to the receiver (assuming 0 dB receiving antenna). The removal of a hopping frequency by designating it unavailable requires adding a hopping frequency to maintain fifteen (15) hopping frequencies.
The frequency designated unavailable remains unavailable for a minimum time equal to 1 second or 5 times the actual number of hopping frequencies multiplied with the channel occupancy time (COT) whichever is longer. No transmission occurs during this time period that the hopping frequency is designated unavailable. After the expiration of this time period of unavailability, the hopping frequency may be evaluated as an ‘available’ frequency.
DAA mechanisms can also employ a wide band modulation other than FHSS. In such a mechanism, a channel is required to be designated unavailable if interference is reported after transmission on that channel. The modulation technique complies with the above non-LBT AFH requirements with the except that a channel must remain unavailable for a minimum time equal to 1 s after which the channel may be considered again as an ‘available’ channel.’
One conventional RAT-independent approach to manage coexistence on the TV WS band is by way of a coexistence manager (CM), whose architecture is set forth by IEEE 802.19 Task group 1 and shown at FIG. 1. The CM is a higher layer function which operates on top of the radio access technologies. As shown in FIG. 1, the coexistence manager interface (CMI) 34 is coupled to a coexistence discovery and information server (CDIS) 32 which collects information on interference levels on the 300-400 MHz frequency band from a TW WS database 42. Also included is a coexistence enabler (CE) 36 which determines which frequency bands in the 300-400 MHz frequency band are available for use by a network or a user device. Information can also be shared with other coexistence managers 38. With the help of the CM, IEEE networks can negotiate the spectrum utilization on the TV WS band between each other or submit to the control of a CM which locally governs the spectrum utilization for the shared spectrum.